Testing, assessment and evaluation (TAE) help teachers and learners measure, control, and monitor the learning process. For some educators TAE oftentimes does not seem to contribute to learning. This paper reports a qualitative action research study that analyses the teenagers’ attitudes and behaviors towards formative assessment, and the use of prior knowledge as a basis to assess English Language Learning (ELL). The study was conducted with an English class at a school in Bogotá.  The pre-service teacher-Researchers collected data about the learners’ engagement or disengagement with English.  The findings suggest that by using Formative Assessment, perceptions towards English learning can change, at the beginning learners were not aware of the role English played in their life; at the end more than half of highlighted the relevance of English in their education.